Method for operating a hybrid vehicle

Abstract

A method for operating a hybrid vehicle having an internal combustion engine and an electric machine, wherein the hybrid vehicle can be driven purely electrically if the internal combustion engine fails because, for example, a fuel tank for supplying the internal combustion engine with fuel is empty. In the event of failure of the internal combustion engine, continued purely electric travel of the hybrid vehicle is made possible only on condition that a restart of the hybrid vehicle is initiated.

What is claimed: 
     
       1. A method for operating a hybrid vehicle having an internal combustion engine and an electric machine, comprising the steps of driving the hybrid vehicle purely electrically if the internal combustion engine fails, wherein in the event of failure of the internal combustion engine, continued purely electric travel of the hybrid vehicle occurs only on condition that a restart of the hybrid vehicle is initiated, wherein the continued purely electric travel of the hybrid vehicle occurs only on condition that an ignition system of the internal combustion engine is first switched off and subsequently switched on again, wherein the continued purely electric travel of the hybrid vehicle occurs only on condition that the failure of the internal combustion engine is due to an empty fuel tank, and wherein the continued purely electric travel of the hybrid vehicle occurs only on condition that an electric energy storage device for supplying the electric machine with electric energy has a sufficient charging capacity. 
     
     
       2. The method as claimed in  claim 1 , wherein the continued purely electric travel of the hybrid vehicle occurs only on condition that the restart is initiated when the hybrid vehicle is stationary. 
     
     
       3. The method as claimed in  claim 1 , wherein the continued purely electric travel of the hybrid vehicle occurs only on condition that a display element is actively requested. 
     
     
       4. The method as claimed in  claim 1 , wherein the continued purely electric travel of the hybrid vehicle is limited in the event of failure of the internal combustion engine, with respect to the rotational speed and the speed of the electric machine. 
     
     
       5. The method as claimed in  claim 1 , wherein in the event of failure of the internal combustion engine in the hybrid vehicle, there is a display indicating that the available driving power is reduced and/or the fuel tank is empty or has to be refilled. 
     
     
       6. The method as claimed in  claim 1 , wherein in the event of failure of the internal combustion engine in the hybrid vehicle, there is a display indicating that the continued purely electric travel of the hybrid vehicle occurs only on condition that the ignition system of the internal combustion engine is first switched off and subsequently switched on again. 
     
     
       7. The method as claimed in  claim 1 , wherein the continued purely electric travel of the hybrid vehicle occurs only on condition that the internal combustion engine is not started after a defined number of starting attempts. 
     
     
       8. The method as claimed in  claim 1 , wherein the internal combustion engine fails if a fuel tank for supplying the internal combustion engine with fuel is empty.